Deadplates are commonly used at the transition point from a first mass conveyor running at one predetermined speed and a second mass conveyor running at a second but higher speed in order to obtain separation of the containers or articles on the conveyor. This is particularly necessary when the next conveyor which the containers will encounter is a vacuum conveyor which will lift the containers up and transport them to another station. The reason for the necessity for speed change is to provide longitudinal separation of the articles so that each properly oriented article will be drawn by the vacuum against the vacuum transfer device, rather than being held by adjacent cans due to the Coanda Effect, which is the wall attachment effect caused by a stream of fast moving air, moving along a surface creating a partial vacuum which tends to draw any adjacent articles toward that surface. While the structure just described is satisfactory for its intended purposes, one of the disadvantages is that it requires substantial room within the plant for the higher speed conveyor and in some plant arrangements, there is simply not enough room for including a second conveyor. The prior art arrangement just described is illustrated in U.S. Pat. No. 3,664,483 to Revaz for "Method of and Apparatus For Releasing Objects to a Transporting Device".
A conventional vacuum transfer device for conveying containers from one elevation to another is disclosed in U.S. Pat. No. 4,136,767 to Sarovich entitled "Vacuum Operated Can-Conveying and Can-Uprighting Apparatus". In this device there is no longitudinal separation of the containers at all. Thus, if one of the containers is held by the other containers due to the Coanda Effect rather than being held by the vacuum, as the containers move around the drum, the weight of the container which is not held by the vacuum may be sufficient to dislodge other containers and cause them to fall off of the vacuum transfer device.
A vacuum transfer apparatus for transferring containers which have already been separated longitudinally is shown in U.S. Pat. No. 4,146,467 to Sauer, et al., entitled "Apparatus for Detecting and Rejecting Downed and Damaged Containers". Thus, in order for this device to operate satisfactorily, there must be provided between the mass conveyor and this device a conveyor which accelerates the containers to provide the necessary longitudinal separation.
Another vacuum transfer device is shown in my U.S. Pat. No. 4,560,060 for "Vacuum Belt Conveyor". In this device, the containers are supplied to the vacuum transfer belt from a mass conveyor in which the containers are in contiguous relationship. The vacuum transfer conveyor operates at a higher speed than the mass conveyor thereby separating the containers as they are moved to a downstream conveyor. The purpose of this separation is to allow the misaligned and damaged containers to be discharged from the apparatus. The device works well for its intended purpose. However, under certain operating conditions, and particularly when the containers are supplied with the open end down, it is possible for a leading container, as it is being drawn up to the vacuum belt, to pull with it one or more trailing containers because of the Coanda Effect whereupon those containers will not be held against the vacuum belt by the vacuum but will tend to fall off. If the containers have not been necked or flanged, the open mouth has a raw edge. When they are being fed with the open mouth down, as they are lifted from the conveyor belt to a faster moving transfer belt, the edge of the open mouth of the container may "trip" on the conveyor belt and tip over or jam which will cause subsequent containers also to be tipped over.
Another vacuum conveyor is shown in my co-pending and commonly owned U.S. application Ser. No. 663,178 filed Oct. 22, 1984 for "Curved Vacuum Transfer Conveyor", now abandoned, wherein containers are transferred from a mass conveyor to a curved vacuum conveyor which picks up the containers and carries them around a curved plenum to a discharge conveyor at a different elevation. With this apparatus the same difficulties just described above can occur. As the leading containers are lifted by the vacuum transfer belt, the upstream containers, trailing on the mass conveyor belt can be drafted along with the leading containers due to the Coanda Effect. Thus, the leading containers are drawn tightly against the vacuum transfer belt, whereas the trailing containers may not. This is a particularly troublesome problem with highly etched bright containers because of the high coefficient of friction between the surfaces of the containers causes them to tend to stick together. As a result, as the containers move around the belt, the weight of the unattached trailing containers can cause them to fall away and pull with them additional containers so that they are not properly transferred to the next downstream station. Furthermore, if the mouths of the containers are down, they can trip on the conveyor belt as they are drafted forwardly causing them to tip over and causing other containers approaching from behind to be tipped over or otherwise disrupted from their normal path of travel.
A vacuum alignment device is provided in U.S. Pat. No. 3,352,404 to Di Settembrini, entitled "Devices for Stabilizing Light Objects on Conveyor Belts" wherein articles are dropped onto a moving conveyor belt from above the belt and a vacuum device is provided to hold the containers in upright condition and to bring them into single file alignment through a guide means. This device is not intended to align containers on a mass conveyor prior to being lifted by a vacuum conveyor.
A form of vacuum deadplate is shown in my co-pending and commonly owned U.S. patent application Ser. No. 700,748 filed Feb. 12, 1985, entitled "Vacuum Single Filer", now U.S. Pat. No. 4,669,604. However, this vacuum deadplate is for the purpose of helping discharge aligned diagonal rows of containers from a mass conveyor in a precise predetermined alignment so that they can be brought into single file alignment along a subsequent vacuum belt. The vacuum deadplate shown therein is not used to hold the containers in a particular alignment prior to being lifted up by a vacuum transfer conveyor belt.
It is often desirable to move containers from a mass conveyor onto pallets in parallel nested rows in contiguous relationship. One such device for accomplishing this arrangement is shown in U.S. Pat. No. 3,300,065 to Witmer, entitled "Means for Material Handling". The containers move from a mass conveyor past converging sidewalls which direct the containers into a palletizing area. The containers move to the distal end of the palletizing area where they are retained by a vertical wall. Succeeding containers move in behind the first containers and fill up the area until the pallet layer is full. One of the difficulties with this arrangement is that sometimes all of the open areas will not be filled in and containers will be missing from one or more locations in a pallet layer when the last row has been filled in. This is caused because the containers do not readily move past each other into the vacant spaces, particularly when the containers have a bright finish which creates a lot of friction between the surfaces of adjacent containers.